Combined prenatal smoking and drinking greatly increases SIDS risk — NIH study

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The National Institutes of Health (NIH)-funded Safe Passage Study on Sudden Infant Death Syndrome (SIDS) found that combined exposures to alcohol and tobacco have a synergistic effect on SIDS risk, given that dual exposure was associated with substantially higher risk than either exposure alone.

Sudden Infant Death Syndrome (SIDS) is the sudden, unexplained, death of an infant under one year of age. Many studies have shown that the risk of SIDS is increased by maternal smoking during pregnancy. Some studies have also found that prenatal alcohol exposure, particularly from heavy drinking during pregnancy, can increase SIDS risk. Now, the National Institutes of Health (NIH)-funded Safe Passage Study provides a look at how SIDS risk is influenced by the timing and amount of prenatal exposure to tobacco and alcohol.

"Ours is the first large-scale prospective study to closely investigate the association between prenatal alcohol and tobacco exposure and the risk of SIDS," said first author Dr Amy J Elliott, of the Avera Health Centre for Paediatric & Community Research in Sioux Falls, South Dakota. "Our findings suggest that combined exposures to alcohol and tobacco have a synergistic effect on SIDS risk, given that dual exposure was associated with substantially higher risk than either exposure alone."

To conduct the study, a multi-centre team of scientists from throughout the US and in South Africa formed the Prenatal Alcohol in SIDS and Stillbirth (PASS) Network. From 2007 until 2015, PASS Network researchers followed the outcomes of nearly 12,000 pregnancies among women from two residential areas in Cape Town, South Africa; and five sites in the US, including two American Indian reservations in South Dakota and North Dakota. The study sites were selected for their high rates of prenatal alcohol use and SIDS, and to include populations where the ethnic and socioeconomic disparities in SIDS remains understudied.

The researchers determined one-year outcomes for about 94% of the pregnancies. They found that 66 infants died during that time, including 28 SIDS deaths and 38 deaths from known causes. In addition to the almost 12-fold increased SIDS risk from combined smoking and drinking beyond the first trimester of pregnancy, they determined that the risk of SIDS was increased five-fold in infants whose mothers reported they continued smoking beyond the first trimester, and four-fold in infants whose mothers reported they continued drinking beyond the first trimester. These risks were in comparison to infants who were either not exposed to tobacco or alcohol during gestation or whose mothers quit tobacco or alcohol use by the end of the first trimester.

"The Safe Passage Study provides important new information about the role of dual exposures to prenatal smoking and drinking as risk factors for SIDS," said co-first author Dr Hannah C Kinney, of the department of pathology at Boston Children's Hospital and Harvard School of Medicine. "Our findings support the current recommendation of the US Centres for Disease Control and Prevention, the US surgeon general, and the World Health Organisation that women not drink or smoke during pregnancy, and emphasises the significance of dual exposure, which provides the greatest risk for infant mortality."

The leaders of the NIH Institutes that provide primary funding for the Safe Passage Study said: "These findings provide still more evidence of the vital importance of the early prenatal environment to healthy postnatal outcomes. Insofar as many women quit drinking and smoking only after they learn that they are pregnant, this study argues strongly for screening for substance use early in pregnancy and intervening as soon as possible. It also calls for stronger public health messaging regarding the dangers of drinking and smoking during pregnancy, and among women who plan to become pregnant."

Background: Sudden infant death syndrome (SIDS) is the leading cause of postneonatal mortality. Although the rate has plateaued, any unexpected death of an infant is a family tragedy thus finding causes and contributors to risk remains a major public health concern. The primary objective of this investigation was to determine patterns of drinking and smoking during pregnancy that increase risk of SIDS.
Methods: The Safe Passage Study was a prospective, multi-center, observational study with 10,088 women, 11,892 pregnancies, and 12,029 fetuses, followed to 1-year post delivery. Subjects were from two sites in Cape Town, South Africa and five United States sites, including two American Indian Reservations. Group-based trajectory modeling was utilized to categorize patterns of drinking and smoking exposure during pregnancy.

Findings: One-year outcome was ascertained in 94·2% infants, with 28 SIDS (2·43/1000) and 38 known causes of death (3·30/1000). The increase in relative risk for SIDS, adjusted for key demographic and clinical characteristics, was 11·79 (98·3% CI: 2·59–53·7, p < 0·001) in infants whose mothers reported both prenatal drinking and smoking beyond the first trimester, 3.95 (98·3% CI: 0·44–35·83, p = 0·14), for drinking only beyond the first trimester and 4·86 (95% CI: 0·97–24·27, p = 0·02) for smoking only beyond the first trimester as compared to those unexposed or reported quitting early in pregnancy.
Interpretation: Infants prenatally exposed to both alcohol and cigarettes continuing beyond the first trimester have a substantially higher risk for SIDS compared to those unexposed, exposed to alcohol or cigarettes alone, or when mother reported quitting early in pregnancy. Given that prenatal drinking and smoking are modifiable risk factors, these results address a major global public health problem.

Amy J Elliott, Hannah C Kinney, Robin L Haynes, Johan D Dempers, Colleen Wright, William P Fifer, Jyoti Angal, Theonia K Boyd, Larry Burd, Elsie Burger, Rebecca D Folkerth, Coen Groenewald, Gary Hankins, Dale Hereld, Howard J Hoffman, Ingrid A Holm, Michael M Myers, Laura L Nelsen, Hein J Odendaal, Julie Petersen, Bradley B Randall, Drucilla J Roberts, Fay Robinson, Pawel Schubert, Mary Ann Sens, Lisa M Sullivan, Tara Tripp, Peter Van Eerden, Shabbir Wadee, Marian Willinger, Daniel Zaharie, Kimberly A Dukes

NIH material

EclinicalMedicine abstract

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